title: The expression of multidrug resistance protein in human gastrointestinal tract carcinomas.
abstract: BACKGROUND
  Multidrug resistance protein (MRP) is a membrane phosphoglycoprotein with an Mr of 190,000 that is involved in the non-P-glycoprotein mediated multidrug resistance of human tumor cells. The aim of this study was to determine the clinicopathologic relevance of MRP expression in human gastrointestinal tract carcinomas.
  
  
  METHODS
  The authors prepared a rabbit antiserum against MRP that does not cross-react with P-glycoprotein and retrospectively examined the expression of MRP in 86 squamous cell carcinomas of the esophagus, 103 adenocarcinomas of the stomach, and 139 colorectal adenocarcinomas by immunohistochemistry. None of the patients in this study had received prior chemotherapy.
  
  
  RESULTS
  The proportion of MRP positive samples in the squamous cell carcinomas of the esophagus (62.8%, 54 of 86) was significantly higher than that in the adenocarcinomas of the stomach (34.1%, 35 of 103) and the colorectal adenocarcinomas (40.3%, 56 of 139) (P <0.01). The proportion of MRP positivity in the well-differentiated carcinomas was significantly higher than that in moderately or poorly differentiated carcinomas. MRP expression was independent of gender, lymph node metastasis, and tumor progression.
  
  
  CONCLUSIONS
  These data indicate that the expression of MRP is correlated with the differentiation of carcinoma cells in the gastrointestinal tract and may be involved in the intrinsic drug resistance of well-differentiated squamous cell carcinoma of the esophagus.
authors.affiliation: Department of Cancer Chemotherapy, Institute for Cancer Research, Faculty of Medicine, Kagoshima University, Sakuragaoka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Takebayashi
authors.forename: S
authors.initials: S
authors.lastname: Akiyama
authors.forename: S
authors.initials: S
authors.lastname: Natsugoe
authors.forename: S
authors.initials: S
authors.lastname: Hokita
authors.forename: K
authors.initials: K
authors.lastname: Niwa
authors.forename: M
authors.initials: M
authors.lastname: Kitazono
authors.forename: T
authors.initials: T
authors.lastname: Sumizawa
authors.forename: A
authors.initials: A
authors.lastname: Tani
authors.forename: T
authors.initials: T
authors.lastname: Furukawa
authors.forename: T
authors.initials: T
authors.lastname: Aikou
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis* / Q000276:immunology; D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D000951:Antigens, Neoplasm / Q000276:immunology; D002294:Carcinoma, Squamous Cell / Q000378:metabolism* / Q000473:pathology; D015179:Colorectal Neoplasms / Q000378:metabolism* / Q000473:pathology; D004938:Esophageal Neoplasms / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000276:immunology; D011817:Rabbits; D012189:Retrospective Studies; D013274:Stomach Neoplasms / Q000378:metabolism* / Q000473:pathology
chemical_list: D018528:ATP-Binding Cassette Transporters; D000951:Antigens, Neoplasm; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins